1. Field of the Invention
This invention relates to filter systems wherein a foreign material is separated from an aqueous flow and more particularly to the separation of highly viscous oils and other tar-like and waxy matter from water in which the oils and matter have become mixed.
2. Prior Art
Means for separating oils from water are well known. For example, an API (American Petroleum Institute) gravity separator has been in use for many years. This separating means relies on the difference in specific gravity of the water and the oil. Oil in the water gradually separates upwardly to float on a surface of the water from where the oil may be skimmed. This type of device is ideal for reducing oil concentration to proximately 150 ppm.
To reduce the concentration of oil to proximately 1-2 ppm, a deep bed type filter containing a bed of a granular filter media has proved effective where the oil has a relatively low viscosity. The filter bed must be periodically rejuvenated to remove the oil collected therein. One preferred manner of filter bed rejuvenation is set forth in U.S. Pat. No. 3,550,774.
When the oil is highly viscous or has a waxy, tar-like, or gluey consistency, the use of the deep bed type filter has heretofore been impractical. Even with the improved means of filter bed rejuvenation as disclosed in the patent cited above, rejuvenation of the filter bed could not be affected.